The present invention relates to a determination method and a machining method of a machined surface of a plate-like material in a surface treatment for obtaining a flat plate-like material having a uniform thickness and minimal machining costs from a plate-like material with two- or three-dimensional deformation, as well as to an apparatus to be used in these methods.
A ceramic sintered plate such as a sputtering target or a metal plate prepared by metal rolling or forging, in most instances, is subject to two- or three-dimensional deformation as a result of thermal stress or machining stress during the manufacturing process. In order to obtain a flat plate-like material having a uniform thickness from a plate-like material with such three-dimensional deformation, machining such as cutting work, grinding, and electrical discharging is performed.
Conventionally, a material with this kind of deformation was subject to the foregoing processes by an operator setting such material directly on a processing machine, or the operator would roughly measure the deformation of the individual plate-like materials in advance with a straight edge or the like, and insert a spacer during the stage of setting such materials in the processing machine in order to maintain flatness. Nevertheless, the current status is that the foregoing methods are conducted based on the operator's instincts.
For instance, when grinding a material based on the operator's instincts, even in the operator is an expert, he/she will need to perform such grinding more than necessary in order to obtain a plane. This is because it will not be possible to maintain the accuracy of flatness or uniform thickness if the operator does not perform such excessive grinding. Therefore, it was necessary to set the machining costs of the material itself higher, and this led to deterioration in the yield. In addition, this also led to increased operation time of the processing machine as a matter of course.
As conventional technology, there are an apparatus capable of precisely measuring the thickness of respective warped plate-shaped works (for instance, refer to Patent Document 1), a warped measuring device comprising a measurement reference unit, a measurement unit, a displacement measurement unit for converting into electrical signals, a warp measure display unit, and a control unit (for instance, refer to Patent Document 2), a manufacturing methods of a ceramic product comprising the steps of pressurizing and molding ceramic material powder, irradiating a light beam on the surface thereof, and measuring the surface status upon receiving the reflected light (for instance, refer to Patent Document 3), a size measurement ceramic gauge provided with a stepwise portion (for instance, refer to Patent Document 4), a plate flatness measuring device comprising a downward measuring unit for measuring the flatness, a plate support pin, a vertical motion actuator, and a pressure regulation unit (for instance, refer to Patent Document 5), and a method for measuring the shape irregularity of a ceramic substrate using infrared thermography (for instance, refer to Patent Document 6).
Nevertheless, the foregoing conventional technologies are methods or devices for measuring flatness, measuring displacement or measuring shape irregularities, and do not provide the concept of improving the yield upon performing surface treatment with machining such as cutting work, grinding, and electrical discharging.    [Patent Document 1] Japanese Patent Laid-Open Publication No. H6-66549    [Patent Document 2] Japanese Examined Patent Application Publication No. S59-36202    [Patent Document 3] Japanese Patent Laid-Open Publication No. S63-173607    [Patent Document 4] Japanese Patent Laid-Open Publication No. H7-128002    [Patent Document 5] Japanese Patent No. 3418819    [Patent Document 6] Japanese Patent No. 3183935